JP3427032B2 - Electret condenser microphone - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electret condenser microphone.

[0002]

2. Description of the Related Art The structure of a conventional electret condenser microphone is shown in FIG. It is made of an electret material in which a face cloth 21 is provided on the top surface of a cylindrical metal case 22 having a sound hole 22a in the central portion, and a metal layer is formed on the surface by vapor deposition or the like via a film ring 23 inside the top surface. Vibrating membrane 24
Is equipped with. The vibrating film 24 includes a fixed electrode 26 and a capacitor spacer 32 via a gap spacer 25.
The concave insulator 27 accommodating the FET 28 and the printed circuit board 29 are disposed further below, and are fixed by the caulking portion 22b of the metal case 22.

The input lead 28a of the FET 28 is connected to the fixed electrode 26, and the output lead 28b penetrates the insulator 7 and the printed board 29 and is connected to the soldered portion 29a on the bottom surface. On the other hand, the vibrating membrane 24 is electrically connected to the metal case 22 by the membrane ring 23.

When a voice is input from the sound hole 22a, the vibrating membrane 24 vibrates, and the capacitance between the vibrating membrane 24 and the fixed electrode 26 changes. Therefore, a voice signal can be obtained by detecting this. You can

[0005]

However, the conventional electret condenser microphone as described above has the following problems.

(1) The electret condenser microphone is required to be small and lightweight, but in the conventional one, the number of parts is large and the thickness of the crimped portion 22b, the soldered portion 29a, etc. cannot be reduced, Further, due to the presence of the insulator 27 and the printed circuit board 29, it was not possible to reduce the size and weight of the entire device.

(2) Since the metal case 22 is fixed by caulking, the airtightness is insufficient, and it is impossible to join the respective parts with solder or solder.

(3) The vibrating membrane 24 is made of a fluorine resin such as FEP or a polyester resin such as Mylar, and its heat resistance is limited. Therefore, the microphone may be bonded to the printed circuit board. It was difficult.

For example, as shown in FIG. 5A, a microphone 40 is provided with a vertical lead 42, and a printed circuit board 4 is provided.
The method of fixing to the through hole 42 of No. 1 has a disadvantage that the through hole 42 needs to be processed and the mounting space becomes large.

Further, as shown in FIG. 5B, in the method of holding the microphone 40 by the socket 43 made of conductive rubber or the like and fixing it to the printed circuit board 41, the socket 43 is expensive and has a large thickness. was there.

Further, as shown in FIG. 5C, the microphone 40 having the lateral leads 44 requires a large area, resulting in poor mounting efficiency. Also, FIG.
Even if the printed board 41 is provided with the flexible sheet 45 and the microphone 40 is fixed to the printed board 41 as shown in (d) and (e), the same large area is required and the mounting efficiency is poor.

[0012]

Therefore, in the present invention, the fixed electrode and the vibrating membrane are arranged at a constant interval, and the voice signal given to the vibrating membrane is detected by the change of the electrostatic capacitance between them. In the electret condenser microphone, a conductive path is formed on the surface of a box-shaped case made of an insulating material, the upper end surface is metallized, the fixed electrode and the vibrating membrane are housed in the box-shaped case, and a metal plate covering them is used. The lid is joined to the metallized portion with a conductive adhesive.

Further, the present invention is characterized in that the box-shaped case is bonded onto a printed circuit board with a conductive adhesive.

Further, the present invention is characterized in that the above-mentioned conductive adhesive is one which cures at 150 ° C. or lower.

That is, according to the present invention, by accommodating each part in a box-shaped case, the size and size are reduced, and the number of parts is reduced, and the lid is joined by a conductive adhesive which cures at a relatively low temperature. Even if a vibrating membrane having low heat resistance is used, each member can be firmly fixed.

Similarly, according to the present invention, a box-shaped case is fixed to a printed circuit board with a conductive adhesive, so that even a vibration film having low heat resistance can be easily surface-mounted with a simple structure. is there.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

The electret condenser microphone shown in FIG. 1 (a) is provided with a recess 9a in a box-shaped case 9 made of ceramics, glass, resin or an insulating material composed of a combination thereof, and the vibration film 4 and the fixed electrode 6 are provided in the recess 9a. And F
A semiconductor element 8 such as an ET or an IC is housed and covered with a plate-shaped lid 2.

The lid 2 is a metal plate having a sound hole 2a in the center, and a vibrating membrane 4 made of an electret material having a metal layer is provided on the step 9b of the recess 9a and a capacitor is provided on the bottom of the recess 9a. A fixed electrode 6 is provided with a gap. Below this, a semiconductor element 8 such as an FET or an IC is housed, and an amplifier circuit or the like is formed in this semiconductor element 8.

Further, the case 9 is provided with a conductive path on the surface and / or inside by printing a conductive paste on the surface, filling through holes, or stacking green sheets having a conductive paste. . First, the lid 2
The conductive path 7a connected to is connected to the electrode lead-out portion 10a on the bottom surface through the outer wall of the box-shaped case 9, and the conductive path 7a also has a function of preventing RF wraparound and static electricity.

The fixed electrode 6 is electrically connected to the conductive path 7b,
The conductive path 7c connected to the input terminal 8a of the semiconductor element 8 and further connected to the output terminal 8b is led out of the box-shaped case 9 and connected to the other electrode lead-out portion 10b.

As shown in FIG. 1 (b), the upper end surface 9c of the box-shaped case 9 is metallized and adhered to the lid body 2 with a conductive adhesive or the like, so that the lid body 2 is electrically conductive.
It is connected to a. The vibrating membrane 4 is electrically connected to the lid body 2 and is connected to the electrode lead-out portion 10a through the lid body 2.

The conductive paths 7a and 7c can be formed inside via through holes. The electrode lead-out portion 10a is grounded, and the other electrode lead-out portion 10b also serves as a power source and an output terminal of the semiconductor element 8.

Now, when a sound is input from the sound hole 2a of the lid body 2, the vibrating membrane 4 vibrates, which changes the electrostatic capacitance between the vibrating membrane 4 and the fixed electrode 6. Therefore, by detecting this, An audio signal can be obtained.

In such an electret condenser microphone of the present invention, by using the box-shaped case 9 made of an insulator, the insulator 27 and the printed board 29 can be eliminated as compared with the conventional structure shown in FIG. Therefore, the number of parts can be reduced and the size can be reduced.

The semiconductor element 8 and the box-shaped case 9 are fixed to each other by using lead-tin solder, gold silicon (AuSi),
A brazing material such as gold tin (AuSn) or gold germanium (AuGe), or a conductive adhesive such as epoxy-based / polyimide-based / polymer-based / silver glass is used. On the other hand, the lid 2 and the box-shaped case 9 are bonded to each other with a conductive adhesive such as an epoxy-based or polymer-based adhesive containing a conductive agent such as silver, which is hardened at room temperature or a relatively low temperature of 150 ° C. or lower. To use. for that reason,
Since the vibrating membrane 4 made of a material having low heat resistance can be used, the microphone can be easily manufactured at low cost.

Alternatively, when assembling the whole as a whole, the semiconductor element 8 and the box-shaped case 9 are fixed by using the above-mentioned low temperature curable conductive adhesive.

As the above-mentioned low temperature curable type conductive adhesive,
A conductive agent such as silver or aluminum is mixed with epoxy-based or polymer-based resin or glass to obtain a volume resistivity of 10 ^-3 to 1
The curing temperature is about 0 ⁻⁵ Ω / cm and the curing temperature is 150 ° C. or less. Here, the curing temperature is set to 150 ° C. or less in order to cure it at a temperature lower than the heat resistant temperature of a fluorine-based resin such as FEP or a polyester-based resin such as Mylar which is a material of a general vibrating film 4.

The electret condenser microphone of the present invention has a box-shaped case 9 as shown in FIG. 1 (c).
Since the electrode lead-out portions 10a and 10b are provided on both sides of the bottom surface of the, the electrode lead-out structure by surface mounting can be facilitated.

That is, by mounting the electret condenser microphone of the present invention on a printed circuit board and fixing it with the above-mentioned low temperature curing type conductive adhesive, it is possible to mount with an extremely simple structure.

Further, the box-shaped case 9 has a rectangular shape in a plan view when viewed from above. Therefore, since there is no waste when the rectangular semiconductor element 8 is housed in the same manner, the overall size can be further reduced. Moreover, when the microphone is mounted on the surface, the square shape facilitates handling and positioning.

As an insulator forming the box-shaped case 9,
Particularly, when a ceramic containing alumina, zirconia, mullite, silicon carbide, silicon nitride, aluminum nitride, etc. as a main component is used, vibration damping characteristics can be particularly improved. That is, since these ceramics have a greater effect of damping vibrations than metal materials and the like, even when used for applications such as mobile phones, it is possible to make it difficult to transmit external vibrations to the inside and improve the performance of the microphone. Can be improved.

Further, since the box-shaped case 9 is used in the present invention, the lid 2 may be in the form of a flat plate, which facilitates the processing. Therefore, as shown in FIG. 1D, for example, a structure having a mesh-shaped sound hole 2a can be adopted. Normally, it is necessary to cover with a face cloth (not shown) or the like in order to prevent foreign matter from entering through the sound hole 2a, but by using the mesh-shaped sound hole 2a in this way, the face cloth can be omitted. it can.

Next, another embodiment of the present invention is shown in FIG.
In this embodiment, the fixed electrode 6 and the lid 2 are combined.

That is, the vibrating film 4 is provided below the lid 2 that covers the upper surface of the box-shaped case 9 with the gap spacer 5 interposed therebetween. The vibrating film 4 is placed on the step portion 9b to form the conductive path 7b and the semiconductor element. 8 and the electrode lead-out part 10b through the conductive path 7c. The lid 2 which also serves as a fixed electrode has a conductive path 7a.
It is connected to the other electrode lead-out part 10a through.

With this structure, the number of parts can be further reduced and the size can be reduced.

In another embodiment, as shown in FIG. 3A, a box-shaped case 9 is provided with two step portions 9b and 9b ', and the semiconductor element 8 is provided on the step portion 9b'. The input lead 8a and the output lead 8b may be placed and connected to the conductive path. Alternatively, as shown in FIGS. 3B and 3C, the semiconductor element 8 having no lead can be used to connect to the conductive path by wire bonding 11.

Further, other electronic equipment can be mounted in the box-shaped case 9. Or if it gets smaller,
In order to prevent the reflected wave of the vibration of the vibrating film 4 from entering the vibrating film 4 again and deteriorating the characteristics, a back chamber may be provided in the recess to widen the space.

Further, when manufacturing the electret condenser microphone of the present invention, it is also possible to manufacture the electret condenser microphone in a state where a large number of box-shaped cases 9 are connected, and finally divide the same.

[0040]

According to the present invention, the electret condenser microphone in which the fixed electrode and the vibrating membrane are arranged at a constant interval and the voice signal given to the vibrating membrane is detected by the change of the electrostatic capacitance between them. In, in the box-shaped case made of an insulating material, the fixed electrode and the vibrating film are housed, and the lid covering them is joined with a conductive adhesive, so that the number of parts can be reduced and the size can be reduced. It can be easily manufactured by using a vibration film having low heat resistance.

As a result, the electret condenser microphone of the present invention can be used in various applications such as an ultra-thin liquid crystal monitor, a card remote controller, a voice memory, and a voice input of a personal computer.

[Brief description of drawings]

1 shows an electret condenser microphone of the present invention, (a) is a vertical sectional view, (b) is a plan view, FIG.
(C) is a bottom view. (D) is a perspective view showing another embodiment of the lid.

FIG. 2 is a vertical cross-sectional view showing another embodiment of the present invention.

3A to 3C are vertical cross-sectional views showing another embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view showing a conventional electret condenser microphone.

5A to 5E are diagrams showing a method of mounting a conventional electret condenser microphone.

[Explanation of symbols]

2: Lid 2a: sound hole 3: Membrane ring 4: Vibration film 5: Gap spacer 6: Fixed electrode 7a-7c: Conductive path 8: Semiconductor element 9: Box type case 9a: concave portion 9b, 9b ': step 9c: Top surface 10a, 10b: Electrode take-out part

Claims (3)

(57) [Claims] 1. A fixed electrode and a vibrating membrane are arranged at a constant interval,
A table of a box-shaped case made of an insulating material in an electret condenser microphone that detects a voice signal applied to a vibrating membrane by a change in capacitance between the two.
Forming a conductive path on the surface and metallizing the upper end surface,
The fixed electrode and the vibrating membrane are stored in the box-shaped case .
And, the main the lid of the metal plate covering them with a conductive adhesive
An electret condenser microphone characterized by being joined to the riser section . 2. The electret condenser microphone according to claim 1, wherein the box-shaped case is bonded onto a printed circuit board with a conductive adhesive. 3. The electret condenser microphone according to claim 1, wherein the conductive adhesive is hardened at 150 ° C. or lower.